Vehicles include a fuel vapor canister to trap diurnal, running loss, and refueling recovery fuel vapors. Such fuel vapor canisters trap the fuel vapors with an adsorbent media, such as activated carbon, and purge the stored fuel vapors to the engine for combustion. However, in hybrid vehicles that are propelled at least periodically by an electric motor and not the engine, the engine may not run for a relatively long duration, particularly after a refueling event has occurred. Because any adsorbed fuel vapors are stored in the canister until the engine can consume them, the long durations between engine operations can lead to high vapor load on the canister, causing bleed-through emissions and other issues. Further, because engine heat is not available during electric operation, the fuel vapor canister may drop in temperature, reducing the efficiency of a subsequent fuel vapor purge.
The inventors herein have recognized the above issues and offer an approach to at least partly address them. In one embodiment, a method comprises initiating a purge of a fuel vapor canister responsive to a temperature profile at a vent side of the fuel vapor canister.
In this way, bleed-through of fuel vapors from the fuel vapor canister may be detected based on a temperature of the canister at the vent side (e.g., at a vent port coupling the canister to atmosphere) of the canister. In one example, the temperature profile may include the temperature of the vent side of the canister increasing as fuel vapors are adsorbed by the adsorbent media of the fuel vapor canister. Then, as the fuel vapor canister becomes saturated, the temperature increase ceases and the temperature then begins to drop as fuel vapors are pushed out/released from the canister. When the temperature stops increasing and starts to decrease (e.g., an inflection point is reached), fuel vapor bleed-through is indicated and the engine may be started to initiate a purge of the fuel vapor canister.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.